start up idle and throttle body

[semlin]

ok, so with lots of recent posts about weird idle results from messing with the throttle bodies on a 93-97, I have a deceptively simple question: can anyone list and describe what systems affect the start up idle on a cruiser with or without ac on? In particular what is it in the throttle body that affects start up idle, and before you say it is dirt inside the the chamber and on the butterfly, please consider that my start up idle dropped dramatically just by re and reing the throttle body to clean my EGR tube without touching the chamber and butterfly. I am wondering does unplugging the TPS or IAC maybe do something?

I am basically confused about what causes the high idle and the crazy high idle when you start with AC on. Originally I heard it was normal and just live with it and I think Idaho Doug mentioned he has had it since new. Then I discovered that removing and cleaning the throttle body can have a dramatic effect, at least for a while. Now it's back again so soon I can't believe it would be necessary to clean the TB again. Just for fun, here is the history of high idle on my truck

1. Dec 93 bought truck with 1500 rpm cold start, 1800 with AC on
2. over a year it built up to 1800 rpm cold start, too scared to try with AC on
3. removed and installed TB to work on EGR but did not touch TB itself and it dropped to 1400 rpm cold start, don't know about AC because it was winter
4. removed TB again and cleaned it, dropped to 1100-1200 cold, 1400 with AC on.
5. 4 months later and now back up to 1400-1500 rpm cold start in morning, 1800 AC on. Weirdly though, after work I start at 1100-1200 rpm even after 12 hours sitting still.

I recently tried just working the throttle back and forth with TB in place to see if that was the cure but it made no difference. Is there maybe a lubricant you can put on the throttle assembly?

 

[e9999]

maybe you just got a frisky rig?
E

 

[lurker]

Semlim,

One thing that really bothers me about the TB issue is the amount of crud inside the intake runners (between the TB and the intake valves, see pic).

If you think about it, all the way from the air cleaner to the inside of the piston cylinder should be clean.

Where is all of this crud coming from?

I suspect it's from the PVC valve cover tube; oil fumes that varnish inside the runners.

If this is true then we basically have a dirty TB that's easilly cleaned, but since the rest of the enviroment is unmaintained (runner and air inlet tubes) maybe this should also be part of our cleaning procedure? We are only addressing 1/2 of the problem? Sort of like cleaning the heart out but it's soon plugged again because no one cleaned the arteries to the heart.

 

[crholliday]

Lurker,

This is an interesting idea. It makes me wonder if maybe the folks that are leaving the TB in place and spraying 17 cans of carb/tb/injector cleaner into the TB arent maybe also cleaning some of that crap out?

My cold start idle hasn't really come down since removing and cleaning mine. Unfortunately I frigged up the baseline when I removed all the attached pieces without paying attention to where they were when I took them off :whoops: So now, no matter what I do, I suspect that I dont have the TPS exactly positioned where it needs to be.... even though the readings were in spec.

C.

 

[semlin]

don't forget the EGR system as a source of al that stuff. It sends recycled unfiltered exhaust gas back into the intake plenum. I have a new EGR valve and year old PCV valve and hoses so I don't think it would be a malfunction of those systems, but I'll admit that the intake chamber and EGR tube wasn't something I would eat off before I buttoned it all up. I think you are proposing that you may have to clean both the intake plenum and the TB to get a longterm fix on start idle or else the built up junk in the intake plenum will re-contaminate the TB. Maybe I will just pull my TB to see if it's dirty again.

 

[lurker]

Lurker,

This is an interesting idea. It makes me wonder if maybe the folks that are leaving the TB in place and spraying 17 cans of carb/tb/injector cleaner into the TB arent maybe also cleaning some of that crap out?

My cold start idle hasn't really come down since removing and cleaning mine. Unfortunately I frigged up the baseline when I removed all the attached pieces without paying attention to where they were when I took them off :whoops: So now, no matter what I do, I suspect that I dont have the TPS exactly positioned where it needs to be.... even though the readings were in spec.

C.

I pulled my TPS off by a lack of brain cells firing in the proper order and I just slapped it back on at about what I thought it was at to start with.

I don't experience the probems that you seem to currently exibit.

I must have totally lucked out or it isn't THAT critical.

 

[Clutchee]

I'm in somewhat the same boat but mine seems to be the Chk Eng. light coming back on after I have cleaned the Throttle body. After cleaning it this weekend we drove approx. 260 miles, no problems then yesterday coming home from getting 35's put on, BAM it came back on-I'm figuring the same code, don't know. Is the throttle body that sensative to build up. In the picture above I cleaned the hole seen at the top of the intake due to being told that was where vacumn flowed from. Trying before to just spray some carb. cleaner into the intake & the light coming back on I can't figure why now it's back.

 

[jesterb]

I posted a thread about a month ago titled "Keep blowing EFI fuses" or something like that. My truck was idleing about the same as yours. I changed out my main EFI relay and now it idles at 1100 cold ac on/ 900 give or take a few, cold ac off. Good luck.

 

[jesterb]

35's .

WTF? I talked to you yesterday and you didn't say a thing about new meats. What did you get?

Sorry to hijack your thread Simlin

 

[cruiserman]

I cleaned everything (throttle body, intake, EGR) out when I did the rebuild, and it made no difference in the startup RPM.

 

[Lars]

I cleaned everything (throttle body, intake, EGR) out when I did the rebuild, and it made no difference in the startup RPM.

I did the same when replacing the head gasket. No changes to startup rpms.


I would have to say this is probably computer related. Does anyone know the startup sequence for these computers? Obviously the computer sets high idle until some type of sender or other electric signal reaches a certain spec and then idle is lowered.

 

[crholliday]

I changed out my main EFI relay

How much does one of those run? Is that the same as the EFI fuse? Sorry I am still FSM deficient.

Thanks,

Chris

 

[jesterb]

How much does one of those run? Is that the same as the EFI fuse? Sorry I am still FSM deficient.

Thanks,

Chris

I think the relay ran me about $12.00 +or- a few dollars from Toyota. It is seperate from the fuse. The fuse is in line before the relay, put there to blow before the relay is damaged. Pull your fuse box in your engine compartment. There is a diagram on the inside of the top.

 

[crholliday]

Jester,

$12 is worth a shot! Anything else to do when changing that out? Or just pull it and stick in the new one?

C.

 

[Scamper]

I'm in somewhat the same boat but mine seems to be the Chk Eng. light coming back on after I have cleaned the Throttle body.

Check to make sure you didn't switch the vac hoses on the EGR modulator when you pulled the TB. Doing so will generate a CEL (two drive-cycle detection).

 

[semlin]

Well that's as clear as mud. We can probably all agree that something some or all of us are doing when we pull the TB does work, sometimes, at least for a while. By process of elimination it is pretty clear that it is not the act of cleaning the chamber, butterfly or intake plenum since people who have done that have not always experienced results and people (well actually me) have also experienced results without doing it. Possible theories are:

1. maybe incidental manipulation of the throttle mechanism during TB removal frees it up somehow?
2. maybe disconnecting the connectors to the TB sensors with the battery still live does something?
3. maybe incidental handling of the air bellows or MAF system does something?
4. maybe evil spirits are being freed from the TB depending on the karma of the wrench

In summary, I don't have a clue

 

[lurker]

Well that's as clear as mud. We can probably all agree that something some or all of us are doing when we pull the TB does work, sometimes, at least for a while. By process of elimination it is pretty clear that it is not the act of cleaning the chamber, butterfly or intake plenum since people who have done that have not always experienced results and people (well actually me) have also experienced results without doing it. Possible theories are:

1. maybe incidental manipulation of the throttle mechanism during TB removal frees it up somehow?
2. maybe disconnecting the connectors to the TB sensors with the battery still live does something?
3. maybe incidental handling of the air bellows or MAF system does something?
4. maybe evil spirits are being freed from the TB depending on the karma of the wrench

In summary, I don't have a clue

"By process of elimination it is pretty clear that it is not the act of cleaning the chamber, butterfly or intake plenum since people who have done that have not always experienced results and people (well actually me) have also experienced results without doing it."

I'm not sure that I would make this statement!

For my case the cleaning of the TB was a world of difference, and as a matter of fact about 10 posters had to beat me over the head before I did it, for I didn't think it would fix what it did either.

If this didn't work of you, you have to consider that the TB and the cables have more than one function, so they can have more that 1 faultly cause. Hence, yes it can be a cable, TPS, IAC, whatever, but they cost money and we're giving you the 90% free solution first, if this doesn't work for you then it's ovious what to do next $$$$$$$$$$$$ .

This is why I preach to REMOVE the TB and do a thought-out cleaning, don't just prop-up the valve body and spray 17 cans of carb cleaner through it and hit it once with a tooth brush and say "I've cleaned my TB, that didn't fix it, what's next?".

BTW I'm not trying to be an expert, for I had my doubts also, but I've seen the light.

 

[jesterb]

Jester,

$12 is worth a shot! Anything else to do when changing that out? Or just pull it and stick in the new one?

C.

Plug and play baby!!

 

[Rookie2]

Plug and play baby!!

Are we talking about the big round knobby EFI relay, a fuse prior/inline to this relay?

Thanks,
Rookie2

 

[jesterb]

Are we talking about the big round knobby EFI relay, a fuse prior/inline to this relay?

Thanks,
Rookie2

Yep; big, round, and knobby